An evolved packet core (EPC) network is a communication network that includes a mobility management entity (MME), a serving gateway (SGW), a packet data network gateway (PGW), a high rate packet data (HRPD) serving gateway (HSGW), and a policy and charging rules function (PCRF). The MME is a key control node for a long term evolution (LTE) access network. Among other things, the MME is responsible for idle mode user equipment (UE) (e.g., mobile handsets) tracking and paging procedures, is involved in the bearer activation and deactivation process, and is also responsible for choosing the SGW for the UE during initial attachment and during intra-LTE handover. The MME is coupled to one or more base stations (e.g., “eNodeBs”) that communicate with one or more UEs.
The SGW routes and forwards user data packets, and acts as a mobility anchor for the user plane during inter-eNodeB handovers, and as an anchor for mobility between LTE and other Third Generation Partnership Project (3GPP) technologies. For idle state UEs, the SGW terminates a downlink data path and triggers paging when downlink data arrives for the UE. The SGW manages and stores UE contexts (e.g. parameters of an Internet protocol (IP) bearer service), network internal routing information, etc.
The PGW provides connectivity from the UE to external packet data networks by being a point of exit and entry of traffic for the UE. The PGW performs policy enforcement, packet filtering for each user, charging support, lawful interception and packet screening, etc. The PGW also acts as the anchor for mobility between 3GPP and non-3GPP technologies, such as WiMAX and code division multiple access (CDMA) technologies.
The HSGW ensures converged mobility management between HRPD (e.g., CDMA) and LTE networks. The HSGW provides interworking between a HRPD access node and the PGW. In some instances, a Packet Data Serving Node (PDSN) can be integrated with or upgraded to the HSGW. The HSGW is coupled to one or more radio network controllers (RNCs or eRNCs) that communicate with one or more base stations.
The PCRF is a device designated for real-time determination of policy rules. For example, the PCRF can activate, in real-time, a set of policy rules to verify access permission, to check and debit credit balances, etc. The PCRF grants users network resources based on user subscriptions and network conditions. For LTE network access, the PCRF is aware of the PGW and the SGW resources because of direct links to (or interfaces with) the PGW and the SGW. For CDMA network access, the PCRF is aware of the HSGW because of a direct link to the HSGW.
During call set up, capacity and/or resources of bearer elements (e.g., the SGW, the PGW, the HSGW) are known to the PCRF (e.g., because of direct links and constant interactions with these bearer elements), but capacity and/or resources of RNCs and/or base stations (e.g., radio access resources) are unknown to the PCRF. When a network (e.g., via the PCRF) grants network resources to a UE for bearer, user, etc. traffic, the radio access resources are not taken into account and it is hoped that the RNCs and/or base stations will allocate appropriate resources. This arrangement works fine when the radio access network has adequate resources. However, during access network congestion (e.g., a base station is having capacity issues or congestion), mobile handsets may experience delays due to additional negotiations (e.g., messages) required to validate resources, and may even experience call failures when required access network resources are unavailable.